Enhanced time zone display

[da-luce]

Currently, we always display the local timezone, regardless of what latitude and longitude are chosen. We should ideally support the following:

• If given a city via the --city option: use the exact time zone of that city
• If given a lat and lon via the lat and lon options: use the timezone of the nearest city
  • Maybe we should just use the local time zone for this option?
    • Would be far simpler to implement
    • Most people are probably using lat and lon to specify their exact location anyways
• If no location is provided: use the local time zone